Volunteers underwent a virtual simulator to test a variety of vibrations to induce drowsiness.RMIT University / Science Daily
If you've ever been guilty of dozing off behind the wheel, it might not be caused by a lack of caffeine or running on little sleep. Researchers recently uncovered a sneaky culprit in people driving while drowsy: car vibrations.
A car's natural vibrations can induce sleepiness in as quick as 15 minutes of getting behind the wheel, the study reports. Researchers from RMIT University in Melbourne, Australia hope the findings can help reduce the 20 percent of fatalities caused by driver fatigue.
"We know 1 in 5 Australians have fallen asleep at the wheel and we know that drowsy driving is a significant issue for road safety," said professor Stephen Robinson. "When you're tired, it doesn't take much to start nodding off and we've found that the gentle vibrations made by car seats as you drive can lull your brain and body."
Robinson said prior to this study, very little was known about the car's effect on sleepiness. Common understandings of why people fell asleep behind the wheel largely stemmed from assumptions of lack of sleep or poor diet or general boredom.
In order to test how various car vibrations affected the performance of drivers, Robinson and associate professor Mohammad Fard used a simulator. They tested 15 volunteers with a virtual simulator designed to replicate the experience of driving on a boring two-lane highway. The visuals would be familiar to anyone who's ever endured a lengthy road trip with very little visual scenery, traffic, or sudden stops.
The simulator itself was built on a platform that vibrated at various frequencies. The volunteers tested their driving alertness on two separate speeds. The first round had vibrations at low frequencies (between 4 to 7 Hz), and the second round had no vibrations at all.
In order to measure drowsiness, the RMIT researchers studied the body's nervous system response as well as heart rate. The vibration enduces sleepiness, which would make it more difficult to think and respond to what's happening on the road. This would put the body's nervous system on alert, and ultimately, lead to a change in heartbeat, the researchers theorized.
The team tracked the volunteers' heart rate variability (HRV) and took note of changes over a 60-minute testing window.
"Our study shows steady vibrations at low frequencies -- the kind we experience when driving cars and trucks -- progressively induce sleepiness even among people who are well rested and healthy," Robinson said, adding that this drowsy sensation can impact driving capabilities much faster than they thought.
"From 15 minutes of getting in the car, drowsiness has already begun to take hold. In half an hour, it's making a significant impact on your ability to stay concentrated and alert."
Drowsiness peaked at the 60 minute point, the researchers reported. Fard said more work and longer driving periods were needed to learn about how car vibrations affected a larger scope of people.
"We want to study a larger cohort, particularly to investigate how age may affect someone's vulnerability to vibration-induced drowsiness as well as the impact of health problems such as sleep apnea," Fard said.
"Our research also suggests that vibrations at some frequencies may have the opposite effect and help keep people awake. So we also want to examine a wider range of frequencies, to inform car designs that could potentially harness those 'good vibrations'."
Robinson said the study could maybe be used in designing car seats that reduced the vibration entirely, finally giving drivers a little bit of a boost when traveling late at night.
"To improve road safety, we hope that future car seat designs can build in features that disrupt this lulling effect and fight vibration-induced sleepiness."